Electronic trim for a variable delivery pump in a hydraulic system for an engine

ABSTRACT

Electronically controlled variable delivery pumps produce output based upon a control signal generated by an electronic control module. The electronic control module includes programming that acknowledges that each pump may have performance characteristics that deviate from a hypothetical nominal pump. Actual pump performance characteristics are then programmed into the electronic control module so that pump control signals are customized or electronically trimmed to suit the performance characteristics of that individual pump. The performance characteristics of the individual pump are gained through testing. The electronic pump trimming strategy of the present invention is particularly applicable to hydraulic systems, such as fuel injection systems, used in internal combustion engines.

TECHNICAL FIELD

The present invention relates generally to variable delivery pumps inhydraulic systems for internal combustion engines, and more particularlyto electronic trimming of variable delivery pumps in hydraulic systems.

BACKGROUND

Hydraulic systems, particularly those used in conjunction with aninternal combustion engine, have been known for years. For example,Caterpillar Inc. of Peoria, Ill. has been successfully manufacturing andselling hydraulic fuel injection systems for many years. In the past,these systems typically included at least one common rail containinghigh pressure actuation fluid that was supplied to actuate a pluralityof hydraulic devices, such as hydraulically actuated fuel injectorsand/or gas exchange valve actuators (engine brake, intake, exhaust). Thehigh pressure common rail was supplied with pressurized actuation fluidby a fixed displacement pump. Control of pressure in the common rail wasmaintained by sizing the pump to always supply more than the neededamount of high pressure fluid and then utilizing a rail pressure controlvalve to spill a portion of the fluid in the common rail back to the lowpressure reservoir. The control system strategy for these systemstypically relied upon a feedback control loop in which the desired railpressure was compared to the measured or estimated rail pressure, andthe position of the rail pressure control valve was set as a function ofthe error signal generated by that comparison. A system of this type isillustrated, for example, in U.S. Pat. No. 5,357,912 to Barnes et al.While these hydraulic systems, and the control thereof, have performedmagnificently for many years, there remains room for improvement.

One area in which these previous hydraulic systems could be improved isby decreasing the amount of pressurized actuation fluid that is spilledback to the low pressure reservoir without performing any useful work,such as actuating one of the hydraulic devices. In other words, energyis consumed and arguably wasted whenever the rail pressure control valveopened to allow pressurized fluid from the high pressure rail to leakback to the low pressure reservoir. In order to decrease the amount ofenergy consumed in controlling the pressure in the hydraulic system, onestrategy has been to introduce a variable delivery pump, and eliminatethe previous rail pressure control valve. Such a hydraulic system isshown and described in co-owned U.S. Pat. No. 6,035,828 to Anderson etal. This system greatly reduces the amount of wasted energy since thepump is controlled to produce only the amount of actuation fluidnecessary to maintain a desired rail pressure. Although this type offluid supply and pressurization strategy has considerable promise, itstill may suffer from at least one subtle drawback when it is controlledvia a feedback loop based upon a comparison of the desired rail pressureto the actual rail pressure. Due at least in part to the fact that thefluid being consumed from the high pressure common rail can be rapidlyand continuously changing, engineers have observed that the controlsystem can be at least temporarily overwhelmed in this highly dynamicsystem. In other words, the system can sometimes demonstrate aninability to both maintain an adequate fluid supply to the hydraulicdevices and do so at the desired pressure without unacceptable lagsbetween the control system response and the fluid demands of thehydraulic devices.

Another potential problem area in controlling these hydraulic systemsusing a variable delivery pump lies in the inevitable fact that eachpump has slightly different performance characteristics. Thesevariations in performance can most often be attributed to thegeometrical tolerance assigned to the various components that make upthe pump. For instance, slight variations in the diametrical clearancesbetween pump pistons and their respective barrels can produce asubstantial and even measurable difference in performance from one pumpto another. Since the control system often operates under the assumptionthat the pump is behaving with performance parameters equal to ahypothetical nominal pump, the timing and accuracy of maintaining adesired pressure in the common rail can sometimes be unacceptably large.In other words, the accuracy and timing of producing a desired railpressure can suffer when the pump deviates in its performance from thatof a nominal pump. One possible strategy for dealing with this problemwould be to attempt to reduce tolerances in the various components to alevel that resulted in pumps having relatively low variability. However,such a strategy may not be viable because of the likely large number ofrejected pumps that would fall outside of the accepted variability rangeand/or potentially costly efforts to reduce component tolerances thatwould be required to produce pumps with low variability.

The present invention is directed to these and other problems associatedwith variable delivery pumps and hydraulic systems.

SUMMARY OF THE INVENTION

In one aspect, a method of preparing an electronically controlledvariable delivery pump for tuning comprises an initial step of testingthe pump at at least one operating condition. The results of the pumptest are then recorded. Finally, information is provided for programmingan electronic control module to adjust a pump control signal based uponthe pump test result.

In another aspect, a method of tuning an electronically controlledvariable delivery pump includes a step of reading data that is afunction of the pump's performance characteristics into an electroniccontrol module. Next, the electronic control module is programmed togenerate pump control signals that are a function of the data. Finally,a control communication link is established between the pump and theelectronic control module.

In still another aspect, a variable delivery pump includes a housingwith an inlet and an outlet. An electronic controller is attached to thehousing. Pump performance data is stored on a data storage device thatis also attached to the pump housing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an engine and hydraulic systemaccording to one aspect of the present invention; and

FIG. 2 are graphs of pump displacement percentage (O) verses controlsignal magnitude (I) for a nominal pump, an example pump as well asexpected lower and upper limits to pump variability.

DETAILED DESCRIPTION

Referring to FIG. 1, an internal combustion engine 9, which ispreferably of the diesel type, includes a hydraulic system 10 thatincludes a pump 11, a high pressure common rail 12 and a plurality ofhydraulic devices 13, 30. Pump 11 can be any suitable variable deliverypump, but is preferably a fixed displacement sleeve metered variabledelivery axial piston pump of the type generally described in co-ownedU.S. Pat. No. 6,035,828. Those skilled in the art, recognize that thesepumps are mechanically actuated, but the output is electronicallycontrolled. Nevertheless, those skilled in the art will appreciate thatany suitable variable delivery pump, such as a variable angle swashplate type pump whose output is controlled via an electrical signal,could be substituted for the illustrated pump without departing from theintended scope of the present invention. The hydraulic system 10includes a plurality of hydraulic devices, which preferably include aplurality of fuel injectors 13, and might also include a plurality ofgas exchange valve actuators 30, such as engine brake actuators, exhaustvalve actuators and/or intake valve actuators.

Fuel injectors 13 are preferably hydraulically actuated fuel injectorsof the type manufactured by Caterpillar Inc. of Peoria, Ill., but couldbe any suitable common rail type fuel injector, or possibly a Bosch typecommon rail fuel injector of the type described in “Heavy Duty DieselEngines—The Potential of Injection Rate Shaping for Optimizing Emissionsand Fuel Consumption”, presented by Messrs Bernd Mahr, Manfred Dürnholz,Wilhelm Polach, and Hermann Grieshaber, Robert Bosch GmbH, Stuttgart,Germany at the 21st International Engine Symposium, May 4-5, 2000,Vienna, Austria. In the illustrated preferred embodiment, the hydraulicsystem 10 utilizes lubricating oil, but those skilled in the art willappreciate that any other fluid could be used, such as diesel fuel(Bosch), depending upon the nature and structure of the hydraulicdevices.

In the preferred embodiment illustrated, variable delivery pump 11 has ahousing 8 which includes an inlet 17 connected to a low pressurereservoir/oil pan via a low pressure supply line 20. An outlet 16 ofvariable delivery pump 11 is fluidly connected to an inlet 27 of highpressure common rail 12 via a high pressure supply line 37. Common rail12 includes a plurality of outlets 28 that are fluidly connected todevice inlets 35 via a plurality of high pressure supply lines 29. Afterbeing used by the respective hydraulic device (fuel injectors 13 and gasexchange valve actuators 30) the used oil returns to low pressurereservoir 14 via an oil return line 25 for recirculation. The systemalso includes, in this example embodiment, a fuel tank 31 that isfluidly connected to fuel injectors 13 via a fuel supply line, which ispreferably at a relatively low pressure relative to that in highpressure common rail 12.

In order to control hydraulic system 10 and the operation of engine 9,an electronic control module 15 receives various sensor inputs, and usesthose sensor inputs and other data to generate control signals, usuallyin the form of a control current level or control signal on-time, tocontrol the various devices, including the variable delivery pump 11,fuel injectors 13 and gas exchange valve actuators 30. In particular, apressure sensor 21 senses pressure somewhere in hydraulic system 10,preferably at high pressure common rail 12, and communicates a pressuresignal to electronic control module 15 via a sensor communication line22. Electronic control module then uses that sensor signal to estimatethe pressure in common rail 12. A speed sensor 23, which is suitablylocated on engine 9, communicates a sensed speed signal to electroniccontrol module 15 via a sensor communication line 24. The electroniccontrol module 15 uses this signal to periodically update its estimateof the engine speed. A temperature sensor 33, which can be located atany suitable location in hydraulic system 10 but preferably in rail 12,communicates an oil temperature sensor signal to electronic controlmodule 15 via a sensor communication line 34. Like the other sensors,electronic control module 15 uses the signal to estimate the oiltemperature in hydraulic system 10. The electronic control modulepreferably combines the temperature estimate with other data, such as anestimate of the grade of the oil in hydraulic system 10, to generate aviscosity estimate for the oil. Those skilled in the art will appreciatethat viscosity estimates can be gained by other means, such as bypressure drop sensors, viscosity sensors, etc. Electronic control module15 controls the activity of fuel injectors 13 in a conventional mannervia an electronic control signal communicated via injector control lines26, only one of which is shown. Likewise, in a similar manner, gasexchange valve actuators 30 are controlled in their operation via anelectronic current signal carried by control communication line(s) 38.In most instances, the ECM actually controls current levels, durationand timing.

Electronic control module 15 could also be considered a portion of apump output controller 19 that includes an electro hydraulic actuator 36and a control communication line 18. Preferably, electro hydraulicactuator 36 controls the output of variable delivery pump 11 inproportion to the electronic current supplied via control communicationline 18 in a conventional manner. For instance, in the preferredembodiment, electro hydraulic actuator 36 moves sleeves surroundingpistons in pump 11 to cover spill ports to adjust the effective strokeof the pump pistons. The pump output controller 19 could be analog, butpreferably includes a digital control strategy that updates all valuesin the system at a suitable rate, such as every so many milliseconds.The pump control signal generated by electronic control module 15 ispreferably a function of the difference between the desired railpressure and the estimated rail pressure, and the estimated consumptionrate of the entire hydraulic system 10.

In order to accurately control fluid pressure in the common rail in thishighly dynamic environment, and do so in a timely manner, it isimportant that the pump behave in a predictable manner to the controlsignals. In the past, the electronic control module assumed that thepump was behaving like a nominal pump, in that at some threshold controlsignal level the pump begins to produce output, and that outputincreases in a known manner in proportion to the magnitude of thecontrol signal. Since it is nearly inevitable that the actual pumpperformance characteristics will deviate to at least some extent fromthe nominal performance characteristics, the present inventioncontemplates the production of pump control signals that take intoaccount the individual pump's performance characteristics. Thus, it isimportant to the operation of the present invention that the actualperformance characteristics of the individual pump be determined, andpreferably a deviation between those measured characteristics andnominal pump characteristics be assessed.

Nominal pump performance characteristics can be determined in anysuitable conventional manner such as by testing and modeling. The pumpperformance characteristics of the individual pumps are preferablydetermined through testing at at least one, and preferably several,operating conditions. By controlling the pump via control signals thatare a function of the pump's individual characteristics, it is believedthat rail pressure can be controlled more accurately and timely becausethe burden on the control system would be reduced. In other words, thecontrol system can concentrate on removing any error between a sensedrail pressure and a desired rail pressure, instead of also having tocompensate for deviations between actual pump performance and anexpected or nominal pump performance. Although the present invention ispreferably implemented by determining how the actual pump deviates froma nominal pump, the present invention could also be implemented inabsolute terms without any reference to a so called nominal pumpperformance characteristic. Which strategy, or a combination of both,depends on the controller algorithm strategy.

Referring now to FIG. 2, a nominal pump performance curve 42 includes anominal threshold control signal 50 and a nominal performance curveslope 51. Thus, when a nominal pump is supplied with a control signalmagnitude (electric current) that is lower than nominal thresholdcontrol signal 50, it produces no output. By knowing the nominalthreshold control signal 50 and the nominal performance curve slope 51,the percent displacement Q can be determined as a function of anycurrent magnitude. The maximum nominal output or 100% Q corresponds to acertain control signal magnitude. Those skilled in the art willrecognize that control signals that exceed that magnitude will have noeffect. In other words, regardless of the control signal magnitude, thenominal pump cannot produce more output than its maximum rated output.Also shown in FIG. 2 are lower boundary curve 40 and upper boundary pumpperformance curve 41 that define the upper and lower variability for theactual performance characteristics of individual pumps. For instance, anactual pump performance curve 43 includes an actual threshold controlsignal 52 and an actual pump performance curve slope 53, which are bothdifferent from those of nominal pump performance curve 42. It should benoted that FIG. 2 is a graph of percent displacement Q rather thanabsolute displacement, which is a function of pump shaft rotation speed,which is generally in turn a function of engine speed. Thus, a thirdmeasurement that illustrates the difference between an actual pumpperformance characteristic and a nominal pump performance characteristicwould be a comparison of absolute volume output at a given percentdisplacement to a nominal absolute volume output at a similar percentagedisplacement. This additional measure might be useful in model basedrail pressure control systems in which absolute pump volume output ismodeled and predicted at all times. Thus, curves 42 and 43 in FIG. 2illustrate that this example actual pump requires a higher than nominalthreshold control signal in order to cause the pump to produce anyoutput, and the pump reaches its maximum output at a control signalsubstantially less than that of a nominal pump. By incorporating thisknowledge into the control strategy, the control system can more quicklyand more accurately control the pump output and hence the rail pressurefor the entire hydraulic system.

Referring back in addition to FIG. 1, each pump is preferably tested byfirst gradually raising the control signal magnitude until it firstbegins producing output. This number corresponds to the actual thresholdcontrol signal 52. The control signal level then can be continuouslyincreased until the pump reaches its maximum output. Assuming a linearrelationship between pump output and control signal magnitude, those twomeasurements should be sufficient to calculate both the actual thresholdcontrol signal 52 and the actual pump performance curve slope 53. Thoseskilled in the art will recognize that the present invention is notlimited to pumps that exhibit a linear relationship between output andcontrol signal magnitude. The two performance characteristics 52 and 53are then recorded. Preferably, these pump characteristics are recordedon a suitable data storage device 45 that is associated with thatindividual pump by being preferably attached to the pump housing 8. Forinstance, the data storage device 45 may be a simple sticker upon whichthe actual threshold control signal 52 is encoded as a first barcode 46on data storage device 45. The slope of the pump performance curve ispreferably stored on data storage device 45 as a second barcode 47. Athird number indicative of a deviation between the actual and nominalpump absolute volume output might be encoded as a third barcode 48 ondata storage device 45. In the preferred embodiment, data storage devicemight be a simple sticker that is attached to the outer surface of thepump. Other data storage devices could be used, including but notlimited to magnetic strips or other machine readable formats. When thepump is actually installed on an engine, the barcodes can be read in anysuitable manner, such as by using an optical barcode scanner in the caseof the example illustration. Those numerical values can then be used toprogram the electronic control module to adjust pump control signals ina way that takes into account the individual pump performancecharacteristics. In addition, if desirable, the absolute volumecharacteristics of the pump may also be utilized, especially in thosecases where the control system uses a pump model, and can be read andprogrammed into the ECM in a similar manner. Finally, the installationis completed by establishing a control communication link between theelectronic control module and the electro hydraulic actuator 36 for thepump output controller.

INDUSTRIAL APPLICABILITY

The present invention finds potential application in any hydraulicsystem, but is particularly applicable to hydraulic systems that includea common rail fuel injection system. When in operation, the pump outputcontroller 19, which includes electronic controller module 15,preferably operates in a conventional digital manner at some suitableexecution rate, such as every so many milliseconds or at some event ratesuch as firing rate. Thus, every so many milliseconds, electroniccontrol module 15 updates its estimates of the rail pressure, the liquidtemperature and the engine speed, which corresponds to the pump shaftrotation rate. In addition, other aspects of the electronic controlmodule are utilizing other sensor inputs and user commands to determinethe amount of fuel that is desired to be injected during a subsequentengine cycle. This desired amount of fuel and the operating condition ofthe engine generally determine what the desired rail pressure should be.Thus, the desired rail pressure is also preferably being updated duringeach computation cycle. Those skilled in the art will appreciate thatnot all aspects of the system need updating every computation cycle.Different parts of the model(s) can operate at different rates dependingon the response of the system. The control system preferably combinesthe estimated system consumption rate with the control rate to arrive ata requested flow rate for the pump that is preferably calculated as apump percentage displacement similar to that graphed in FIG. 2. Thisrequested percentage displacement is then truncated in the event that itexceeds the maximum possible output rate for the pump. This requestedpump percentage displacement is then converted into a pump controlcurrent that is used to adjust the position of the electro hydrauliccontroller 36 to make variable delivery pump 11 produce an outputdisplacement percentage corresponding to the requested pump displacementpercentage. Before being sent to the pump, the pump control signal isadjusted so that the control signal corresponds to the displacementpercentage requested for that actual pump rather than for a nominalpump.

Those skilled in the art will recognize that, depending upon thecharacteristics of the individual hydraulic system, the structure of thepump and how it is controlled as well as the overall control systemstrategy, an implementation of the present invention into otherhydraulic systems could look substantially different. For instance, thepump might be biased to produce its maximum output when no controlsignal is present, rather than no output as in the example illustratedpump. Furthermore, the relationship between control signal magnitude andpump output may not be linear. In addition, the sophistication level ofthe present invention could go well beyond that illustrated in theexample embodiment. For instance, it might be desirable to determine howindividual pumps deviate in performance from a nominal pump as afunction of other variables, such as fluid viscosity, temperature,speed, ambient pressure, etc. Depending on the performance demands ofthe individual hydraulic system, the level of sophistication in applyingthe concepts of the present invention can be adjusted in complexity tomeet the specific demands of each individual system.

Those skilled in the art will recognize that the present inventionprovides the ability to control system pressure in a more accurate andtimely manner. It is believed that a consequence of such control shouldbe more accurate control over injection performance, likely resulting ina lowering of undesirable engine emissions while improving overallengine performance. The present invention also has the ability to reducecosts by allowing pumps with a wider range of variability to beacceptable for use in hydraulic systems. The reason being that, althoughthe individual pump may vary substantially from the performance of anominal pump, one can accommodate for this deviation by appropriatetrimming of control signals generated by the electronic control module.Thus, the present invention has the ability to not only improveperformance but also reduce costs by reducing the number of pumps thatneed to be scrapped or reworked in order to become acceptable.Furthermore, the present invention also has the potential ability tofurther reduce costs by allowing the individual geometrical tolerancesfor pump components to be relaxed.

When in operation, the electronic control module senses rail pressureand determines a correction is needed. It then commands a change ofcontrol current to the pump, waits during the sampling period, checksthe pressure again and changes current to the pump again if necessary.This sampling and waiting mode of pressure correction continues untilthe pressure in a rail matches the desired pressure. Each displacementcontrol pump generally has three distinct performancecharacteristics: 1. a threshold or minimum current to begin displacementchanges (also known as a starting or minimum) current, the gain slope(displacement verses current percent Q/I, see FIG. 2), and ending ormaximum current. The current range or the range over which control ispossible is the ending current minus the starting current. Any currentinputs outside of these two points or outside of this range have noimpact upon the action of the pump. Therefore, any time the electroniccontrol module makes current inputs beyond this range, it wastes ormisuses that particular sampling period. That misuse of time can causehigher emissions and reduce engine performance. Only when the ECMcommands inputs inside of the control range is the sampling period beingused efficiently.

As stated above, each pump is different than the rest, having in theexample embodiment, three unique performance characteristics. Because ofthis, the ECM may know the effective current range for a nominal pump,but unless the present invention is implemented, the ECM does not knowthe effective current range for the individual pump in its hydraulicsystem. The present invention has the potential to eliminate the needfor the ECM to go beyond the actual current range of the pump via use ofthe programmed ECM software. The three number code can be stamped on thepump like a barcode or other suitable code and then scanned into theengine software. Each numeral can be used to describe one of the threeperformance characteristics. The software can then use the code todetermine the actual operating characteristics of the pump. With theseoperating characteristics, the ECM modifies the appropriate softwareparameters to achieve improved hydraulic system performance, which willresult in a reduction in undesirable emissions and an improvement toengine performance.

In addition to the electronic trimming strategy described above withregard to the example hydraulic system, other potential pumpcharacteristics can also be encoded and scanned into the engine controlmodule to further increase the speed and accuracy of the hydraulicsystem control. For instance, the ratio of actual pump performance tonominal pump performance or volumetric efficiency could be determined asa function of fluid pressure, as a function of oiltemperature/viscosity, as a function of percentage displacement of thepump, as a function of differing pump inlet pressures, which correspondto the engine lubricating oil pressure, and possibly even as function ofthe oil bulk modulus. As discussed above, one new engine controlstrategy called a model based control attempts to calculate the oilusage of the hydraulically actuated fuel injectors and/or engine brakes,and 2) calculate the required current to the pump to provide that oilflow based upon engine speed, pump outlet pressure, oil viscosity (oroil temperature) oil bulk modulus, geometric displacement of the pump,and lube oil pressure. Based upon these perameters, the engine controlwould likely initially default to the calculated nominal current, andthen make minor adjustments to maintain or control rail pressure using aconventional feedback control strategy. An extra code that could bestamped on the pump is the percent flow at a given speed when comparedto a nominal pump. For instance, a nominal pump may produce 40 LPM at3000 RPM. As a pump has completed the assembly and test sequence, theflow at 3000 RPM may be 41.2 LPM. This pump would be considered 103% ofnominal. This code could be stamped or otherwise attached to the housingfor the pump and then scanned into the engine control module, therebyincreasing the accuracy of the flow calculations and subsequent currentpredictions.

Those skilled in the art will appreciate that the present invention hasbeen described in the example context of a Caterpillar Inc. typehydraulic fuel injection system. The present invention is alsoapplicable to other types of common rail systems, such as the BoschAPCRS fuel system identified in “Heavy Duty Diesel Engines—The Potentialof Injection Rate Shaping for Optimizing Emissions and FuelConsumption”, presented by Messrs. Bernd Mahr, Manfred Durnholz, WilhelmPolach, and Hermann Grieshaber, Robert Bosch GmbH, Stuttgart, Germany,at the 21^(st) International Engine Symposium, May 4-5, 2000, Vienna,Austria.

Those skilled in the art will appreciate that various modificationscould be made to the illustrated embodiment without departing from theintended scope of the present invention. For instance, the presentinvention can also be used in other hydraulic applications outside therealm of hydraulic fuel injection systems. Applications requiring speedcontrol (such as a machine with a hydrostatic transmission or ahydraulic cylinder on an injection molding machine) and torque orhorsepower controlled machines (limiting the pressure and volume ofdischarge to prevent the pump from using more power than the prime movercan provide, could benefit from an implementation of the presentinvention to their control strategy. For instance, performance and/orgain curves (current verses power/actual discharge flow/torque) can beplotted and encoded into the engine electronic control module or otherelectronic device. Thus, other aspects, objects and advantages of thisinvention can be obtained from a study of the drawings, the disclosureand the appended claims.

LIST OF ELEMENTS

TITLE: ELECTRONIC TRIM FOR A VARIABLE DELIVERY PUMP IN A HYDRAULICSYSTEM FOR AN ENGINE

FILE: CAT FILE 01-243

-   8. Housing-   9. Engine-   10. Hydraulic System-   11. Variable Delivery Pump-   12. Common Rail-   13. Fuel Injectors-   14. Low Pressure Reservoir/Oil Pan-   15. Electronic Control Module-   16. Outlet-   17. Inlet-   18. Control Communication Line-   19. Pump Output Controller-   20. Low Pressure Supply Line-   21. Pressure Sensor-   22. Sensor Communication Line-   23. Speed Sensor-   24. Sensor Communication Line-   25. Oil Return Line-   26. Injector Control Line-   27. Inlet-   28. Outlet-   29. High Pressure Supply Line-   30. Gas Exchange Valve Actuator-   31. Fuel Tank-   32. Fuel Supply Line-   33. Temperature Sensor-   34. Sensor Communication Line-   35. Device Inlet-   36. Electro Hydraulic Actuator-   37. High Pressure Supply Line-   38. Control Communication Line-   40. Lower Boundary of Pump Performance Curves-   41. Upper Boundary of Pump Performance Curves-   42. Nominal Pump Performance Curve-   43. Actual Pump Performance Curve-   50. Nominal Threshold Control Signal-   51. Nominal Performance Curve Slope-   52. Actual Threshold Control Signal-   53. Actual Pump Performance Curve Slope

1-20. (canceled)
 21. A method of preparing a mechanically actuatedelectronically controlled variable delivery pump for tuning beforeinstallation in a fluid system, comprising the steps of: testing atleast one pump operating condition at least in part by mechanicallypowering the pump while supplying a pump controller with a predeterminedelectronic control signal; recording at least one pump test resultindicative of an output flow rate magnitude from the pump; determininginformation for programming an electronic controller of a fluid systemto adjust a pump control signal based upon the pump test result.
 22. Themethod of claim 21 including a step of attaching coded information basedon the pump test result to the pump.
 23. The method of claim 22 whereinsaid attaching step includes a step of attaching a bar code to the pump.24. The method of claim 21 wherein said testing step includes a step ofdetermining a threshold control signal at which the pump begins toproduce output.
 25. The method of claim 21 wherein the determining stepincludes a step of determining a shape of a function curve relatingcontrol signal magnitude to pump output rate magnitude.
 26. The methodof claim 25 wherein the determining step includes a step of estimating alinear relationship between a control signal and a pump output ratemagnitude that includes an intercept and a slope.
 27. The method ofclaim 21 including a step of comparing the pump test result to anexpected pump result; and the information includes data that is afunction of a difference between the expected pump result and the pumptest result.
 28. The method of claim 21 wherein the information includesfirst data that is a function of a threshold control signal at which thepump begins to produce output, second data that is a function of a curveslope relating control signal magnitude to pump output rate magnitude,and third data that is a function of a maximum control signal magnitudebeyond which the pump produces no additional output.
 29. A method ofinstalling a mechanically actuated electronically controlled variabledelivery pump, in a fluid system, comprising the steps of: fluidlyconnecting an inlet and an outlet of the pump to the fluid system;reading data that is based on test results of the pump's performancecharacteristics from a data storage device associated with the pump;programming an electronic controller to generate pump control signalsthat are a function of the data; and establishing a controlcommunication link between a pump controller of the pump and theelectronic controller.
 30. The method of claim 29 wherein the readingstep includes a step of scanning coded information from a code attachedto the pump.
 31. The method of claim 30 wherein the scanning stepincludes a step of scanning a bar code attached to the pump.
 32. Themethod of claim 29 wherein the programming step includes adjusting apump model.
 33. The method of claim 29 wherein the programming stepincludes a step of setting a threshold control signal at which the pumpbegins to produce output.
 34. The method of claim 29 wherein theprogramming step includes a step of setting a slope of a linearrelationship between control signal magnitude and pump output ratemagnitude.
 35. The method of claim 29 including a step of attaching thepump to an engine.
 36. A variable delivery pump comprising: a housingwith an inlet and an outlet; an electronic controller attached to saidhousing; and a data storage device attached to said housing; and pumpperformance data stored on said data storage device in a machinereadable format, wherein the data is based upon a pump output flow ratemagnitude test result.
 37. The pump of claim 36 wherein said datastorage device includes a bar code.
 38. The pump of claim 36 whereinsaid pump performance data includes a threshold control signal at whichsaid pump begins to produce output.
 39. The pump of claim 36 whereinsaid pump performance data includes a curve slope relating controlsignal magnitude to pump output rate magnitude.
 40. The pump of claim 36wherein said pump performance data includes data that is a function of amaximum control signal magnitude beyond which the pump produces noadditional output.